Sticky, I would rather add high-flow cats than delete them for a non-track only car. Yes, it would still be cheaper than the Ericsson.

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Originally Posted by camaross305

Yea but that exhaust is also $12,000

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Originally Posted by gthirtyfizle

Thats what i mean. But that extra power comes with an 11K price tag lol. Not many ppl would spend that kind of money for an extra 5-10hp. As u can see most ppl that would are the same ones that are putting stroker kits on their M's...

I know, I know, its f*cking expensive. I just wanted to point out the TQ gain(Due to the High flow cat) which is nice. In a way, its like buying an Omega Vs Patek Philippe, both tell the same time but the Patek Philippe cost 10X more....

Slammed, at the moment I think AA would be the best. Maybe Evosport too but Im not familiar with their chip. I heard someone here say, if you take the car to you dealer and get new sofware added, AA will reflash the ECU once on twice free, but you would have to confirm with them.

yup, biggest gains on the m3 are found by deleting the cat and chipping to remap engine to freer flowing exhaust...

the bmw engineers had to pull a few tricks out of the bag to make this car meet California emissions standards (anyone notice how rough the car idles when cold? this is why...)

without knowing too much about the subject, I could safely say defeating some of these emissions controls (i.e Cat and o2 sensors) you would unlock some relatively significant gains (40-50hp) at the cost of making your car non-street legal .... then again, will cops really catch you on this?

yup, biggest gains on the m3 are found by deleting the cat and chipping to remap engine to freer flowing exhaust...

the bmw engineers had to pull a few tricks out of the bag to make this car meet California emissions standards (anyone notice how rough the car idles when cold? this is why...)

without knowing too much about the subject, I could safely say defeating some of these emissions controls (i.e Cat and o2 sensors) you would unlock some relatively significant gains (40-50hp) at the cost of making your car non-street legal .... then again, will cops really catch you on this?

Well, you are correct with your guess and Turner deletes the pre-cats and tunes for that. 40 wheel gain, very significant.

Anyway, the car will be legal still with one set of cats, as in passing emissions. Tampering with any cat is illegal I think, but I don't know the exact regulations on this and they can vary by state.

I am getting a custom exhaust with a custom tune next week, I'll have more info.

However, *if* I were to remove the primary cats, I would get a CEL. *If* I did that, I would need software to turn it off. While getting the CEL turned off, *if* my car found its way onto the dyno, I could get a new tune that took the primary cat delete into account for more power.

Chipping isn't worth it, imo. If you ever have a serious problem and you chipped your car, you might be out of a warranty. That would suck, and when you weigh the risk versus the minimal gain the choice is clear.

Invest into your own driving skill first, as others have mentioned. There is no reason to take a razor blade and sharpen it if your just going to hand it to a bear and let him swing it around. Not to mention you will also be giving up fuel economy. This isn't something for nothing.

so deleting the cats would actually make a significant power gain?
and if I do decide to remove the cats...I should do that before tuning with AA. so they can tune the software precisely and properly towards having better exhaust flow?
Is that correct?

so deleting the cats would actually make a significant power gain?
and if I do decide to remove the cats...I should do that before tuning with AA. so they can tune the software precisely and properly towards having better exhaust flow?
Is that correct?

I don't know if AA has a tune for the cat delete, I would assume they do.

You probably don't want to run catless, just without one set, decide if you want the first or second set gone.

whats the difference between getting rid of first or second cat?
Also..how would it sound?

Don't know how the sound would differ vs. one or the other. If removing a cat, expect it to be louder.

The first set is right off the header. In my opinion, this is the greatest restriction in our exhaust system. When aftermarket headers come, you can be sure they will delete the first cat. Deleting this cat, is what I think makes the most power for the aftermarket headers for the S85. I believe this will carry over to the S65.

Turner, for example, just deletes the first set off cats off the newer M's and provides matching software that is equal to gains with aftermarket headers.

The secondary cat is easier to delete and does not give a CEL. It can be done without a complimentary tune. It is further down stream.

Your sick on the 335 part... You can mod a m3 to get to 500hp..without it falling apart.. Look at pg post's ... a exhaust ,pulley , AA software...Getting 465,,470.. Being stingy on the number's.....with a cost of 6k.... How much $$$ would a 335 cost to get it to 414????

it's key that you get the software matching the cat-delete....and defeat the o2 sensors as well, otherwise you'll get check engine lights all the time, and potentially put your car into "limp home" mode...

Those two cans to the left of the picture (probably right off the headers) look like cats too. The #1 item is labeled as cats too. I'd be surprised if there were no cats right off the headers since that seems to be the norm for newer BMW's in oder to get the first set hot ASAP.

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Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."

You sure about this? I'm pretty sure there's only one catalytic converter on our cars, followed by a silenser, followed by a resonator. We looked very closely at all of the exhaust pieces that came off of my car, and there was only one set of catalytic converters. I'm open to the idea that I'm wrong here because we didn't actually cut all of the pieces apart and take a look inside. But based on weight alone (catalytic converters are heavy), there was only one section that appeared to be catalytic converters.

SLAMMEDM3 - I had my ECU reprogrammed and I love it. I had the car dyno's and I did gain about 30hp. The shop said I may not feel the difference however I do feel the difference in Torque. That is the biggest difference I feel. At lower end RPM's the car is more responsive and doesn't feel as slug ash as some people talked about when they first owned the car. I also have new pully's and an exhaust.

I used a local guy in Arizona. I did consider Active and ESS however I wanted a local person just in case there was an issue. I paid $1,200 and I would do it again.

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The Verdict: Every other manufacturer should give up on building their own cars and just make M3s instead. -Car and Driver June 2008

SLAMMEDM3 - I had my ECU reprogrammed and I love it. I had the car dyno's and I did gain about 30hp. The shop said I may not feel the difference however I do feel the difference in Torque. That is the biggest difference I feel. At lower end RPM's the car is more responsive and doesn't feel as slug ash as some people talked about when they first owned the car. I also have new pully's and an exhaust.

I used a local guy in Arizona. I did consider Active and ESS however I wanted a local person just in case there was an issue. I paid $1,200 and I would do it again.

Nice!! I did the same (I mean, us a local guy) for my ECU and I suppose when I can most "feel" some difference is when I drive another M3.

You sure about this? I'm pretty sure there's only one catalytic converter on our cars, followed by a silenser, followed by a resonator. We looked very closely at all of the exhaust pieces that came off of my car, and there was only one set of catalytic converters. I'm open to the idea that I'm wrong here because we didn't actually cut all of the pieces apart and take a look inside. But based on weight alone (catalytic converters are heavy), there was only one section that appeared to be catalytic converters.

The first set is a pre-cat of sort. If you look under the car, where your cats were removed were the main cats which are further down stream.

Starting with the E46 M3, in the US market, BMW incorporated a pre-cat or primary cat, into the header. The reason for it, is it heats the fastest due to its location. It also saps power and the Euro E46 M3 did not have it due to different emissions regulations. This was part of the reason of the different HP ratings between the euro M3 and the US M3 (also due to different standards.)

I had the car on the lift the other day and was checking it out. Right where the header finishes there is a small bend and then you have the first set. This is the cat I would want to remove while leaving the "main" or secondary cat in.

Most X-pipes replace the secondary and leave the cat off the header in place.

Turner has realized the cheapest and best upgrade is removing this first cat and tuning for it. They did this for the M5/M6, and now the M3.

You can see what I am talking about here, the first set bolts up to the header, followed downstream by the second set, and then followed by the resonator (just checked the link you sent, its the same photo):